(a) Field of the invention
The present invention relates to a chelating polymer.
(B) Description of the prior art
As polymers having a chelating ability for removing heavy metals, styrene-divinylbenzene copolymer resin having an imino diacetic acid group [--N(CH.sub.2 COOH).sub.2 ] or polyamine group [--(NHCH.sub.2 CH.sub.2).sub.n NH.sub.2 ], and thiourea type resins or dithio carbamic acid type resins produced by introducing into phenolic resins a coordinate group such as sulfur and nitrogen having a higher affinity with heavy metals have been heretofore well known. However, these polymers have a lower heavy metal ion adsorbing (exchanging) ability and a lower adsorbing (exchanging velocity. They are expensive from the cost point of view and once they adsorbed heavy metals, there is a difficulty in removing the adsorbed heavy metals therefrom. Recently, the reactivity of a mercapto group was recognized and was used to produce chelating polymers by introducing a mercapto group into cellulose. Although these polymers are attractive, they are still in laboratorial investigation and far from being of practical use.